The first position should be directly between your ears
The rest of them are kind of whatever start with a small box and make it bigger and find a averaging cube that you like
The smaller the box the more tight the average will be, the bigger the box the more lively the sound will be at the end because it will get more of the room
so you’re still looking for a dead accuracy go with a small box if you’re looking for overall better sound quality for yourself and everyone else go with a bigger box
That is without explaining things to technically